p16INK4a inhibition with toosendanin alleviates pulmonary fibrosis by restoring autophagic flux

Effective therapies for Idiopathic Pulmonary Fibrosis (IPF), a progressive and fatal lung disease, are critically lacking. While both cellular senescence and autophagy are implicated in IPF pathogenesis, the precise mechanisms linking them to fibrosis progression remain poorly understood. Current treatments often fail to halt disease progression, highlighting an urgent need for novel therapeutic targets. This research addresses the gap by investigating the crosstalk between senescence and autophagy, specifically focusing on how their dysfunction contributes to extracellular matrix remodeling in IPF.

Researchers conducted patient-derived transcriptomic analysis, followed by studies in naturally aging mice and mouse models of bleomycin (BLM)- and radiation-induced pulmonary fibrosis. They investigated the role of p16INK4a (p16) through genetic depletion experiments, independent of p21Cip1. Subsequently, they screened antifibrotic compounds from Melia azedarach fruit extracts, identifying toosendanin. This compound was then tested for its ability to suppress p16 promoter activity, restore autophagic flux, and attenuate BLM-induced pulmonary fibrosis in vivo. Further validation involved testing the p16 promoter inhibitor abyssinone II and activator neorautenol.

Patient-derived transcriptomic analysis revealed a strong association between enhanced extracellular matrix remodeling, cellular senescence, and autophagic dysfunction in IPF. Elevated expression of p16INK4a was correlated with impaired autophagic flux in naturally aging mice, BLM- and radiation-induced pulmonary fibrosis mouse models, and lung tissues from IPF patients. Genetic depletion of p16 reduced pulmonary fibrosis and preserved autophagic flux in response to fibrotic challenge, independent of p21Cip1. This confirmed p16's critical role. Screening identified toosendanin, which effectively suppressed p16 promoter activity, restored autophagic flux, and attenuated BLM-induced pulmonary fibrosis in vivo. > The p16 promoter inhibitor abyssinone II alleviated both autophagy dysfunction and fibrosis progression, while the promoter activator neorautenol exacerbated both phenotypes, demonstrating p16 acts as a key regulatory node in the crosstalk between senescence and autophagy dysfunction.